The COSMOS survey (artist's impression)

When the slices across the Universe and back into time are combined, they make a three-dimensional map of dark matter in the Universe. The three axes of the box correspond to sky position (in right ascension and declination), and distance from the Earth increasing from left to right (as measured by cosmological redshift). Note how the clumping of the dark matter becomes more pronounced, moving right to left across the volume map, from the early Universe to the more recent Universe.